The present invention relates to a process for making penicillamine and its hydrochloride. D,L-penicillamine hydrochloride has been made by hydrolysis of the corresponding thiazolidine-4-carboxylic acid ester with a semiconcentrated hydrochloric acid and a yield of about 90%. Through purification the crude penicillamine is converted with acetone to the tetramethyl-thiazolidine-4-carboxylic acid which subsequently is again split to form the pure D,L-penicillamine hydrochloride.
The thiazolidine-4-carboxylic acid ester could however be obtained only in small yields directly from the corresponding thiazolidine-4-carbonitrile or by way of the 2.2.5.5-tetramethyl-thiazolidine-4-carbonamide-hydrochloride. The tetramethyl-thiazolidine-4-carboxylic acid heretofore could not be formed directly by saponification of the corresponding thiazolidine-4-carbonitrile.
It has also been proposed to form thiazolidine-4--carbonitriles from thiazolines-.DELTA..sup.3 by addition of HCN. The thiazolidines-.DELTA..sup.3 in this case were obtained by reacting ketones with sulfur and ammonia. In a reference relating to the reaction with aldehydes yields are obtained only of 10% of thiazolines-.DELTA..sup.3, see the Annual Report for 1967 of Landesamt fuer Forschung des Landes Nordrhein-Westfalen, pp. 11-35.
It has accordingly not been possible to obtain penicillamine in an industrially acceptable manner in high yields starting from easily accessible starting products.
It is an object of the present invention to provide for a process of making penicillamine which solves this problem.